A means of enhancing the effectiveness of post-emergent herbicides comprises the addition of an effective amount of at least one carboxylic acid diester to a post-emergent herbicide.
Herbicides are generally classified into two groupsxe2x80x94those having significant foliar use and those primarily applied into the soil. Herbicides with significant foliar use, generally described as post-emergent herbicides, are further divided into three major categories based on translocation patterns and initial plant symptoms: (a) translocated herbicides showing initial symptoms on new growth; (b) translocated herbicides showing initial symptoms on older growth; and (c) non-translocated herbicides showing initial localized injury. Each of these categories may further be subdivided according to herbicidal mode of action, i.e., auxin-type growth regulators; aromatic amino acid (EPSDS) inhibitors; branched-chain amino acid (ALS/AHAS) inhibitors; carotenoid pigment inhibitors; lipid biosynthesis (ACCase) inhibitors; organic arsenicals; xe2x80x9cclassicalxe2x80x9d photosynthesis inhibitors; xe2x80x9crapidly actingxe2x80x9d photosynthesis inhibitors; Photosystem I (PSI) energized cell membrane destroyers; protoporphyrinogen oxidase [Protox (PPO)] inhibitors; and glutamine synthesis inhibitors. Of these, the most popular are glyphosate and salts of glyphosate including the monoammonium, diammonium and isopropyl ammonium salts disclosed in U.S. Pat. Nos. 5,998,332; 4,507,250; 4,481,026; 4,405,531; 4,315,765; 4,140,513; 3,977,860; 3,799,580; and 3,853,530 (including the commercial products Roundup(copyright) and Touchdown(copyright)), sulfonylurea, (sold under the tradename Classic(copyright) by E.I. duPont de Nemours and Co.), glufosinate, first reported as a herbicide in Schwerdtle, et. al. xe2x80x9cZ. Pflanzenkr. Pfanzenschutz. Sonderheft IX. p. 431 (and now including the commercial product Finale(copyright)), oxyfluorfen, disclosed in U.S. Pat. No. 3,798,276 (and now commercially sold as Goal(copyright)), imazamox, discovered by American Cyanamid (now commercially available as Raptor(copyright)), clethodim, first reported by Kincade, et. al. in Proc. Br. Crop Prot. Conf. Weeds in 1987 (now commercially sold as Select(copyright)), sethoxydim, discovered by Nippon Soda in Japan (now commercially sold as Poast(copyright)), quizalofop, disclosed in U.S. Pat. No. 4,629,493 (now commercially sold as Assure(copyright)), fenoxaprop, first reported by Bieringer, et. al. in Proc. Br. Crop Prot. Conf. Weeds in 1982 (now commercially sold as Fusion(copyright) and Acclaim), fluazifop, disclosed in British Patent 1,599,121 (now commercially sold as Horizon 2000 and Fusilade DX) and bipyridilium salts first disclosed in British Patent 813,531 (commercially sold as Paraquat(copyright) and Diquat(copyright)) amongst others.
Post-emergent herbicides are generally slow acting and usually take days or even weeks to show a visual effect on the weeds and grasses to which they have been applied. This is undesirable from the user""s standpoint. U.S. Pat. No. 5,994,269 discloses a means of achieving a more rapid visual sign of herbicidal activity by the addition of an activator to glyphosate. However, the time to achieve the desired effect is too long. Furthermore, the disclosed method does not permit the use of less post-emergent herbicide. Alternatives are therefore needed.
Along with the need to obtain a faster time for visualization of the herbicidal effect, it is further desired to develop a means which mandates less of the herbicidal active ingredient than is now employed. The reduction in the amount of the herbicidal active ingredient is desired since such chemicals are generally toxic and non-biodegradable.
It has been discovered that the herbicidal activity of post-emergent herbicides is enhanced by the addition, to the post-emergent herbicide, of least one carboxylic acid diester of the formula:
ROOC(CH2)nCOORxe2x80x2xe2x80x83xe2x80x83(I)
wherein R and Rxe2x80x2 are independently selected from a C1 to C4 alkyl group and n is from about 5 to about 9. These diesters are based on acids occurring in nature and thus have low toxicity and high biodegradability. Further, the introduction of such diesters to a post-emergent solution, emulsion or suspension permits utilization of reduced amounts of the post-emergent herbicide while still providing effective weed control. Additionally, use of the composition of the invention reduces the time required for systemic phytotoxic symptoms to appear on the target weed.
In accordance with the method of the invention, diesters of C7 to C11 linear dibasic acids, usually in admixture with a surfactant or emulsifier, are added to a herbicidal composition and the resulting mixture is applied to the target weed. The target weed starts to wilt and turn brown within hours. Necrosis has been seen, for instance when dimethyl azelate is added to glyphosate, to approach 100% within twenty-four to thirty-six hours of treatment compared to minimal necrosis times of three to four days without the diester.
The effectiveness of post-emergent herbicides is dramatically improved by addition of a compound of formula (I) to a post-emergent herbicide prior to its application to the vegetation. The compound of formula (I) is at least one carboxylic acid diester of the formula:
ROOC(CH2)nCOORxe2x80x2xe2x80x83xe2x80x83(I)
wherein R and Rxe2x80x2 are independently selected from a C1 to C4 alkyl group and n is from about 5 to about 9. R and Rxe2x80x2 on any given compound of formula (I) may be the same or different alkyl group. In a preferred embodiment, n is 7 or 8. Particularly desirable esters are the dimethyl, diethyl, diisopropyl and dibutyl esters. Especially preferred as the carboxylic acid diester of formula (I) are the lower alkyl diesters of pimelic, suberic, azelaic, sebacic and undecanedioic acids, for example, the methyl or ethyl esters. Mixtures of two or more of the carboxylic acid diesters may further be employed.
The composition applied to the vegetation of the invention may further contain a diluent. Any liquid in which formula (I) is soluble or miscible may be employed as a diluent. As a post-emergent, the herbicidal compositions of the invention are preferably applied to the locus of the unwanted vegetation as an aqueous mixture or emulsion.
When a compound of the formula (I) is added to a post-emergent herbicidal composition
(a) either as a water emulsion or
(b) by diluting a commercial herbicidal concentrate to a herbicidally effective concentration [with a water emulsion of formula (I)]
and the resulting mixture is applied to weeds according to the herbicide manufacturers recommendation, the weeds exhibit a visual phytotoxic effect in less time than would be obtained with the herbicide in the absence of the compound of formula (I). As an example, weed and grass necrosis may approach 100% within 24 hrs. with glyphosate in combination with dimethyl azelate, compared to 3-4 days or longer without the addition of dimethyl azelate.
Furthermore, with the addition of a compound of formula (I) such as dimethyl azelate, to the post-emergent herbicide, less of the post-emergent herbicide than specified by the manufacturer can be used to achieve the same herbicidal result as would be obtained using the herbicide suppliers"" recommended amount in the absence of dimethyl azelate.
The herbicidal composition of the invention containing a compound of formula (I) may be applied to the locus of the unwanted vegetation in effective amounts in the manner normally used with the herbicide without the addition of the compound of formula (I). Concentrations of the post-emergent herbicide in the herbicidal composition of the invention will vary depending on the herbicide and the weeds to be controlled but the concentration of the compound of formula (I) in the final herbicidal composition is preferably between from about 0.5 to about 5.0 % by weight of the herbicidal composition, preferably between from about 1.5% to about 3.0% by weight. This preferred amount of compound of formula (I) is independent of the selection of post-emergent herbicide in the composition. Thus, regardless if the post-emergent herbicide is a sulfonyl urea, which typically is used in amounts approximating 5 to 10 grams per acre, or glyphosate, which typically is used in agricultural sprays in amounts approximating 0.75 to 1.0 weight percent, the amount of compound of formula (I) in the final herbicidal composition is between from about 0.50 to about 5.0 weight percent of the herbicidal composition.
Any post-mergent herbicide, regardless of its mode of action, may be used in combination with the carboxylic acid diester of formula (I). These include those translocated herbicides showing initial symptoms on new growth (Table I); translocated herbicides showing initial symptoms on older growth (Table II); and non-translocated herbicides showing initial localized injury (Table III), as set forth in Ross and Lembi, Applied Weed Science, 2d edition, Prentice-Hall, 1999, pp. 156-157:
Particularly desirable results have been evidenced in herbicidal compositions containing the compound of formula (I) and phenoxy acids, such as 2,4-D; glyphosates (N-phosphonomethylglycines) and ammonium (particularly monoammonium and diammonium) and isopropylammonium salts thereof; glufosinate and salts thereof, sulfonyl urea herbicides, especially rimsulfuron containing herbicides; cyclohexanediones, such as sethoxydim containing herbicides; benzothiadiazole herbicides; diphenylether herbicides especially those containing fomesafen; and bipyridilium herbicides, such as paraquat and diquat.
The method of the invention may be used to control established vegetation in the vicinity of a seeded crop or in a weed concentrate area by contacting the foliage of the unwanted vegetation with the herbicidal composition.
Surfactants, wetting agents, dispersing agents, suspending agents, and/or emulsifying agents may further be employed with the herbicidal composition of the invention. Such materials are typically included in commercial herbicidal formulations, to which may be added the compound of formula (I).
Unwanted vegetation may be killed by applying to the locus of the vegetation the herbicidal composition of the invention. The herbicidal composition of the invention may be contacted with the unwanted vegetation by spraying or otherwise distributing the composition onto the foliage in accordance with the manufacturers"" directions of the post-emergent herbicide [to which has been added the carboxylic acid diester of formula (I)]. The herbicides of the invention exhibit several advantages not previously seen with other commercial herbicides. Most importantly, the invention dramatically reduces the kill time. Leaves of vegetation sprayed with herbicidal compositions of the invention usually start to shrivel or turn brown within hours of a single application. Necrosis is evident, usually in 24 hours. Typically unwanted vegetation is dead in less than 24 hours compared to 3 to 4 days when the post-emergent is solely used. Since use of the compound of formula (I) decreases the amount of post-emergent herbicide required, the invention dramatically reduces costs.
Weeds and grasses which may be killed by use of the herbicidal composition of the invention include quack grass, buttercup, common cinquefoil, multi flora rose, common yellow woodsorrel, prostrate spurge, henbit, poison ivy, poison hemlock, common speedwell, broadleaf plantain, Japanese honeysuckle, dandelion, wild violet, Bermuda grass, nutsedge, wild garlic, knotweed, red sorrel, lambs quarters, pokeweed, carpetweed, crabgrass, buckhom plantain, nimblewill, or common chickweed. Moss, small tree saplings and suckers and shoots from tree roots and tree stumps may also be controlled with the emulsion.